Add InitialPeers class for manging initial peers

include/InitialPeers.php

@@ -0,0 +1,81 @@
+<?php
+
+namespace Arionum;
+
+/**
+ * Class InitialPeers
+ */
+final class InitialPeers
+{
+    public const MINIMUM_PEERS_REQUIRED = 2;
+    public const PRELOAD_ERROR = 'Unable to retrieve peers from the preload list.';
+    public const PRELOAD_LIST = 'https://www.arionum.com/peers.txt';
+
+    /**
+     * @var array
+     */
+    private $peerList = [];
+
+    /**
+     * InitialPeers constructor.
+     * @param array|null $peerList
+     * @return void
+     */
+    public function __construct(?array $peerList = [])
+    {
+        $this->peerList = $peerList;
+    }
+
+    /**
+     * Retrieve a peer from the initial peer list.
+     * @return string
+     * @throws Exception
+     */
+    public function get(): string
+    {
+        if (!$this->peerList || count($this->peerList) < self::MINIMUM_PEERS_REQUIRED) {
+            $this->retrieveFromPreloadList();
+        }
+
+        return $this->selectPeer();
+    }
+
+    /**
+     * Retrieve all available initial peers.
+     * @return array
+     * @throws Exception
+     */
+    public function getAll(): array
+    {
+        if (!$this->peerList || count($this->peerList) < self::MINIMUM_PEERS_REQUIRED) {
+            $this->retrieveFromPreloadList();
+        }
+
+        return $this->peerList;
+    }
+
+    /**
+     * @return string
+     */
+    private function selectPeer(): string
+    {
+        return $this->peerList[array_rand($this->peerList)];
+    }
+
+    /**
+     * Retrieve a peer from
+     *
+     * @return void
+     * @throws Exception
+     */
+    private function retrieveFromPreloadList(): void
+    {
+        $peerList = file(self::PRELOAD_LIST, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
+
+        if (!$peerList || count($peerList) < self::MINIMUM_PEERS_REQUIRED) {
+            throw new Exception(self::PRELOAD_ERROR);
+        }
+
+        $this->peerList = $peerList;
+    }
+}